The Sanborn Map Company held a near total monopoly of fire insurance maps in the United States from the 1870s through to the 1970s. The maps were used by fire insurance company underwriters to assess the cost of coverage and the risks. As cities grew in size throughout the nineteenth century, it became harder for individual insurance companies to visit places personally to make such assessments, so mapping companies were formed to produce reliable, detailed surveys of risks instead.
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| Banner for the 1892 Sanborn-Perris Map Company map for Santa Cruz and Camp Capitola. [Library of Congress] |
Most of the Sanborn company's maps were hand-drawn at a scale of 1:600 or 50 feet per inch on 21" by 25" paper. They were also color coded in various ways to differentiate lower risk features (yellow), areas of high interest (red), and areas of extreme risk (teal), as well as sources of water (blue). As the maps became more advanced, other important features were added such as the routes of water mains and electrical lines. The company focused primarily on cities and towns, so many smaller settlements were skipped. That being said, if a specific business was large enough, it would sometimes feature as an addendum to the nearest settlement with a map. As cities and towns grew, the number of maps representing that settlement were expanded with the largest cities encompassing hundreds of pages by the end.
The company was named after Daniel Alfred Sanborn, who began drawing fire insurance maps in 1866 in Tennessee. In 1867, he moved to New York City and founded the D. A. Sanborn National Insurance Diagram Bureau and drew maps for Boston and other towns in New England. Over the next fifty years, Sanborn began buying out all of his competition, culminating in a monopoly of the industry after the last rival was bought out in 1916. By the mid-1920s, the company employed 300 field surveyors and 400 other staff to produce, print, and sell the maps. Yet it was this monopoly that led to the company's ultimate failure. Unable to keep up with demand and charging high prices for its services, Sanborn became the target of government and corporate attempts to rein the company in. The Great Depression did the job for them, though, and survey work dropped by two-thirds. By the 1950s, many insurance companies began bypassing Sanborn using a system called line carding, which had already been used for structures that did not appear on maps. Basically, individual structures each had a card with a summary of its risks, thereby not requiring a map to access it. This combined with improved building codes, construction methods, and fire protection equipment meant that maps were just not needed anymore. The last new map was produced in 1961 and the last updated map in 1977.
Ways of using this source:
Sanborn maps became an imperfect tool for envisioning the past layout of American cities in a poorly-photographed era. As early as the 1960s, historical societies began collecting maps for local history uses and by the 1980s, it became one of the key resources uses in identifying the history of certain areas. And there are good reasons for that! Original Sanborn maps were extraordinarily detailed and contained unique information not easily found elsewhere.
The first step in using these maps is to find the key or index for the year you are researching. Until the 1920s, most of the maps had an Index map as its first page. It would highlight areas of the city with numbers that correspond to pages of the map series. For smaller settlements, the first page also usually contained a portion of the actual map. In later years, a separate index page with the names of settlements and major businesses was included. These would also reflect changes between versions of the map.
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| Excerpt of a Sanborn Map of the lower plaza of Santa Cruz, 1883. [Library of Congress] |
Each map had a wide range of features useful to researchers. For example, this 1883 map of Santa Cruz shows most of the major structures in downtown, as well as early street names and even physical dimensions of features such as the widths of lots and streets. Vacant or abandoned buildings are usually marked as such, while homes—marked "dwg" for dwelling—are scattered across the map. The high risk structures in teal include a paint shops, blacksmith shop, carpentry shop, wagon shop, and candyshop. Buildings with fire protection in red include the St. Charles Hotel, the Pacific Ocean House, the Masonic Hall and adjacent public hall, and a dwelling off Mission Street. And sources of water in blue include hydrants on Locus Street, Park Street, Cherry Street, Vine Street, and Pacific Avenue, and an elevated water tower behind the Pacific Ocean House. Large and important businesses have their names on them, as well, providing good reference information for researchers.
Railroad historians benefit from the fact that mainline tracks are included on Sanborn maps and nearly all railroad (but not streetcar) trackage appears on maps prior to 1900. Other railroad-related features such as stations, depots, tunnels, sheds, car and engine houses, turntables, and water towers also appear. In the map above, almost all of the South Pacific Coast Railroad and Southern Pacific Railroad depots on Cherry and Park Streets are shown, and these largely match photographic evidence from the same period. Sanborn maps also often show or suggest businesses that used the railroad.
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| Excerpt of a 1905 Sanborn Map showing the Santa Cruz Union Depot yard, 1905. [Library of Congress] |
This map of the Union Depot yard in 1905 shows several customers of the railroad as well as several other important items. Williamson & Garrett had a warehouse at the end of a spur shared by the Standard Oil Company. Beside these was a large lumber yard owned by the Santa Cruz Planning Mill, which had a warehouse just to the south. Another mill was across Washington Street from this while a third was across Chestnut Street, owned by Sinkinson. Although railroad tracks are not showing going to any of these, their location beside the tracks suggests strongly that they used the railroad and, furthermore, increases the likelihood that private railroad spurs catered to them. This is even implied by the platform listed beside the Santa Cruz Planing Mill warehouse on Washington Street. Southern Pacific-owned spurs, such as that catering to Williamson & Garrett, were usually included on maps, but private ones were inconsistently included.
Other interesting details can also be gleaned from this map. Williamson & Garrett had a 5-foot-deep platform that ran between its warehouse and the spur and it mostly stored lime, cement, and grain feed in the warehouse. Standard Oil kept two oil tank cars on bricks beside the tracks. Sinkinson's mill produced lumber, novelty goods, and shingles, and Sinkinson himself lived on the property. Meanwhile, the Santa Cruz Planing Mill owned several large structures and produced mouldings, sashes, doors, dressed lumber, and standard lumber, and it kept a night watchman on site. The surrounding lumber yard could support approximately 1,000,000 board feet of lumber!
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| Layout of streets and railroad rights-of-way derived largely from the 1877 Sanborn Map superimposed atop a modern Google Map. [Derek R. Whaley] |
Perhaps the most important feature of Sanborn Maps, however, is that they document change—sometimes substantial—in a community. By comparing several years of maps with later, more modern sources of information, entirely new outlooks on city planning and development can be discovered. The map above was composed by comparing the layout of streets near the Santa Cruz waterfront from 1877 and today. It shows several streets that have been renamed or shifted, and several other streets that did not exist yet in 1877. It also shows the impact of the railroad on the area now known as Blackburn Terrace.
Downsides and problems with this source:
Precision was never a goal of Sanborn maps. The maps often demonstrated a mildly idealized version of a city rather than reality. Roads often did not stick precisely to the outlined alignment and distortions at the edges of the maps were very common, although these usually can only be discovered when they are placed next to other maps or overlaid on a modern map of the same area. Many smaller or insubstantial structures were also left off, as well as streetcar tracks and railroad sidings and spurs (except in the pre-1890 maps). In addition, geographic features were usually not specified unless they presented a risk or were a source of water, which means elevations and other topographical features were left off maps.
Most problematic, though, was the technique of "pasting-up" old maps in order to update them. Until around 1910, almost all maps produced by Sanborn were originals, as in they were redrawn fresh for every new survey. However, the company began cutting corners in the 1910s and instead of producing new maps, updated old maps using pasted-on revisions that hired pasters would apply to maps purchased by people. Often new maps would be created at the same time to cover areas that had substantial changes or had not been surveyed before, but pasted-up maps became the norm from the 1910s onward and this caused a lot of problems for researchers because demolished buildings would often be left on maps and railroad trackage was not altered to reflect changes in alignments. Business names also were not always changed. The end result is that pasted-up maps are not nearly as useful for historians as original maps and must be treated with caution.
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| Excerpt of a 1917 Sanborn Map showing the area around the former railroad depots in Santa Cruz. [University of California, Santa Cruz, Legacy Digital Collections] |
The map above is a 1905 map that was "pasted-up" for a 1917 update. The useful aspects of the map are the new structures that have been added, including several new buildings on Vine and Division Streets and an ice house and storage shed beside the tracks off Rincon Street. But there are several issues, too. The tracks still show narrow-gauge and broad-gauge because they reflect the trackage before the lines were standardized in 1908. As such, the ice house sits directly atop a track on the map and it is unclear if any track still followed that route at all. The tunnel, too, does not reflect its actual dimensions since it was also enlarged. Another odd aspect of these paste-ups is that building angles are not always applied perfectly, especially when there's nothing adjacent to the paste-up. For example, you can see a corner of Santa Cruz High School in the 1883 map above at the top edge of the map. Its entry stairway is almost perfectly parallel with the page. The angle of the page doesn't change in the 1917 version, but the school is now rotated about 30 degrees in the photograph. Is this a new school? Was the old school rotated? Why was a paste-up required for a building of largely the same dimensions? These types of questions cannot be answered by Sanborn maps.
Local History Resources:
Library of Congress, Sanborn Maps Collection
(https://www.loc.gov/collections/sanborn-maps):
The collection held by the Library of Congress is extensive, full color, and spans much of the country. But due to copyrights, it also doesn't have everything available online so you will have to visit Washington, D.C. to see the whole collection. The good news is that there are many free maps available for download at good resolutions.
- Alviso: 1908
- Aptos: 1888, 1892, 1908
- Ben Lomond: 1908
- Boulder Creek: 1892, 1897, 1908
- Campbell: 1899, 1905, 1908, 1920
- Castroville: 1892, 1910, 1929
- Cupertino: 1920
- Felton: 1895, 1908
- Gilroy: 1886, 1892, 1906
- Gonzales: 1886, 1892, 1903, 1910
- Hollister: 1886, 1892, 1902, 1910
- King City: 1888, 1890, 1892, 1903, 1910, 1919
- Los Gatos: 1884, 1888, 1891, 1895, 1904, 1908
- Mayfield: 1884, 1888, 1894, 1904
- Milpitas: 1893, 1908
- Monterey: 1885, 1888, 1892, 1905, 1912, 1912
- Morgan Hill: 1908
- Mountain View: 1888, 1891, 1897, 1904, 1908, 1921
- Pacific Grove: 1888, 1892, 1897, 1905, 1914
- Palo Alto: 1895, 1897, 1901, 1904, 1908
- Salinas: 1886, 1892, 1900, 1913
- San Jose: 1884, 1891, 1915, 1950
- San Juan Bautista: 1908, 1926, 1929
- Santa Clara: 1887
- Santa Cruz: 1886, 1888, 1892, 1905
- Saratoga: 1918
- Soledad: 1888, 1892, 1910
- Soquel: 1888, 1892, 1908
- Spreckels: 1919
- Sunnyvale: 1908, 1911, 1930
- Tres Pinos: 1888, 1892, 1895, 1910, 1930
- Watsonville: 1888, 1892, 1902, 1908, 1920, 1962
University of California, Santa Cruz, Legacy Digital Collections
(http://digitalcollections.ucsc.edu/digital/collection/p15130coll3/search/searchterm/sanborn):
For many years, the UCSC collection of maps was the go-to place for local historians, but the collection pales in comparison to the Library of Congress site and the October 2020 refresh of the Legacy Digital Collections website removed the ability to download maps, making the site even less useful. Still, there are several maps and versions of maps that aren't available online from the Library of Congress and the website navigation is still relatively easy. Furthermore, high resolution versions can be viewed on the website.
- Aptos: 1888, 1892, 1908
- Ben Lomond: 1908
- Boulder Creek: 1892, 1897, 1901, 1908
- Campbell: 1899, 1905
- Castroville: 1892, 1910, 1913
- Felton: 1895, 1908, 1918
- Gilroy: 1886, 1892, 1906
- Gonzales: 1886, 1892, 1903
- King City: 1888, 1890, 1892, 1903
- Los Gatos: 1888, 1891, 1895, 1904
- Mayfield (Palo Alto): 1888, 1894, 1904
- Milpitas: 1893
- Mountain View: 1888, 1891, 1897, 1904
- Palo Alto: 1895, 1897, 1901, 1904
- San Jose: 1884, 1891
- Santa Clara: 1887,
- Santa Cruz (including Capitola): 1877, 1883, 1886, 1888, 1892, 1905, 1917
- Soquel: 1888, 1892, 1908, 1911
- Watsonville (including Pajaro): 1873, 1886, 1888, 1892, 1902, 1904, 1908, 1911, 1920
(https://www.losgatosca.gov/42/Los-Gatos-Library):
(https://about.proquest.com/products-services/databases/sanborn.html):
(https://edrnet.com/prods/sanborn-maps/):
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